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25 янв 2022


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25 янв 2022
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    Wire Drawing Machines

    Wire drawing is an important industrial process. Wires are reduced in diameter through a series of die/capstan combinations which provide the desired reduction steps. Typical copper wire drawing machine within BICC Cables Ltd use up to twenty-one dies in one line and it is necessary to optimise the die drafting for each machine and final wire diameter to obtain good machine efficiency and high quality product. An important aspect in the manufacturing process is to avoid wire breakages with the resultant loss of production due to short final lengths and the associated time required to restring the drawing machine. In order to optimise the conditions for each machine and wire size, computer simulations of the process are used to predict performance by estimating factors such as the ratio of drawing stress to ultimate tensile stress, drawing force, back tension and heat generated.

    A computer simulation of the multi-line wire drawing process for copper wire has been modelled by the Wrexham Technology Centre of BICC Cables Ltd using a bulk model. The redundant work during the drawing process was included by formulation and equations for the redundant deformation were derived that were in good agreement with published experimental work.

    A new computer simulation has been developed to predict the performance of wire drawing process. The model uses a one dimensional explicit finite difference method to determine the plastic deformation in the dies. The redundant work formulation was used as in the previous simulation. This paper describes the numerical methods used and compared the results from the new computer simulation with the previous bulk model. Significant differences are predicted in the stress ratios, drawing force and heat generated for process predictions. The new simulation of the plastic deformation in the dies also indicated optimum semi-die angles away from the traditional eight degrees.

    After having reduced the diameter as much as possible by hot rolling (smallest diameter approximately 5.5 mm), smaller diameters must be produced by cold drawing (see Golis et al., 1999; Schruff, 2004). Tension is applied to draw the hot rolled wire in several pulls down to a final required diameter between 1 and 2 mm. Calcium and sodium stearate are usually applied as a drawing lubricant. These soaps are particularly suitable at high drawing speeds because the lubricant film remains intact. Due to friction, temperatures above 150 °C and as high as 400 °C develop, which cannot be reduced by the cooling effect of the lubricant and air alone. Thus the dies are cooled with water and the wire with compressed air. Compared with earlier machines, modern dry wire drawing machines are more efficient with regard to the consumption of cooling water and lubricant as well as the filtration of stearate dust emissions. Dry aluminum wire drawing machine are machines that pull in the forward direction (Ruge and Wohlfahrt, 2001; Schimpke et al., 1977). They pull the wire as many as 14 times, i.e. a series of 14 drawing dies which are usually powered separately using rotational speed regulators. Typical technical data may be found in Table 22.4.

    Applications include electric motor drives for conveyors and other material handling equipment such as stacker reclaimers, crushers, haulages, ball mills, cranes, hammer mills, rotary dryers, centrifuges, reciprocating pumps, winches, fans and wire drawing machines.

    In view of their easy adaptability, they are manufactured in standard sizes suitable for common types of load applications. They are therefore available on short deliveries, in smaller ranges, say, from 1 kW to 200 kW. They can be selected for the required service conditions, as a motor is selected to suit a particular load requirement from the available sizes of couplings.

    2 Variable-filling or scoop control-type couplings (variable-speed couplings) (Figure 8.7)

    Through such couplings the output speed of the runner can be changed by varying the volume of oil in the working circuit through the scoop operating lever, as shown in Figure 8.7(b). When the oil volume is full, slip is at minimum and the output speed is maximum. As the oil circuit is emptied, the slip gradually increases. A constant-speed motor can thus be used to provide a stepless variable-speed drive. Speed variation is possible up to 15–20% of Nr for centrifugal loads such as fans and pumps.

    The control of wire temperature is very important in the fine wire drawing process. The wire speed should be increased, and the wire temperature should be dropped as much as possible. Up to now, the process design of wire drawing process depends on the experiences of experts. In this study, a wire drawing process design method was proposed to increase the productivity. The proposed method of this study includes the pass schedule and the design of a multi pass wire drawing machine. A pass schedule was performed based on the calculation of the wire temperature. Also, a new multi pass brass wire drawing machine was manufactured to apply the designed pass schedule. Through the wire drawing experiment, the effectiveness of the proposed process design method was evaluated. The final drawing speed was increased from 1,100m/min to 2,000m/min without deterioration of final drawn wire.

    It is a non-slip dry continuous drawing machine with integrable wire; in the drawing process, the steel wire and the surface of the reel do not slide in the circumferential direction of the reel, and the wear of the two surfaces is relatively small. And when a reel in the middle is temporarily stopped, the reel behind it can still work for a period of time as usual depending on the amount of line accumulation. This model has the advantages of simple structure, convenient operation and maintenance, and low manufacturing cost. At the same time, it has a certain line accumulation coefficient, and the steel wire stays on the coil for a long time, which is conducive to the sufficient cooling of the steel wire. However, there are more wire guide wheels, which not only increases the number of bending of the steel wire, but also the product and pay-off of the reel cause the steel wire to twist along its axis during the drawing process, which seriously affects the internal quality and surface quality of the steel wire.

    The characteristics of the pulley type wire drawing machine determines that this model is only suitable for drawing medium and small specifications, and relatively low quality and strength requirements for steel wire and other metal wires.

    Double reel type wire drawing machine

    Because the steel wire will be twisted during the drawing process of the pulley type wire drawing machine, a double drum type wire drawing machine was developed on the basis of the pulley type wire drawing machine. This model has the advantages of a pulley wire drawing machine, and eliminates the torsion phenomenon of the steel wire in the drawing process, and the cooling effect of the steel wire on the drum is better.

      The double-drum wire drawing machine is the same as the pulley wire drawing machine. There are more guide wheels, especially the middle thread guide wheel between the upper and lower drums, which produces 180 when the steel wire passes through it. Because it is bent, it is not suitable for drawing large-size and high-strength steel wire; the operation of the machine is not as convenient as the pulley type, and the friction ring between the upper and lower reel and the wire wheel and other parts have a large moment of inertia, which limits the improvement of the drawing speed. This model is a transitional model developed from a pulley-type wire drawing machine to a higher-level wire drawing machine, suitable for drawing medium and small-sized steel wires.

       Looper wire drawing machine

    In order to further improve the quality and drawing speed of the steel wire, a looper-type wire drawing machine was developed. It is also a non-sliding wire drawing machine; it simplifies the route of the steel wire between the reels. Axial torsion is generated, and due to the use of a DC motor to drive, a large range of stepless speed regulation can be realized, which expands the selection range of elongation between the reels, and the wire drawing machine can run in the most reasonable working state. Moreover, the looper generates a pulling force or a counter-pulling force on each reel during the drawing process. In the drawing with looper tension and looper reverse tension, it can reduce the drawing force, prolong the life of the wire drawing die and reduce the consumption of kinetic energy. The looper type wire drawing machine is a continuous wire drawing machine that can automatically adjust the speed. Theoretically speaking, within the tolerance limit of the steel wire to the compression rate and the mechanical energy parameters of the machine, as long as the total process compression rate is greater than or equal to the total compression rate of the machine, the machine can automatically adjust the drawing process for any process. . Therefore, the looper type wire drawing machine is a relatively advanced wire drawing machine, suitable for drawing small and medium-sized high-strength steel wires and alloy steel wires.

    The disadvantage of the looper wire drawing machine is that due to the use of DC drive, the electric speed control system is complicated, the manufacturing cost of the machine is high, and the maintenance is difficult. The looper tension needs to be adjusted when drawing wires of different specifications; therefore, the operation of the machine The technical level is relatively high. In addition, this model has many thread guide wheels, thread threading is more complicated, and the steel wire has many bending times, so it is not possible to draw large-size steel wires and hard materials.

    straight wire drawing machine

    Pulley type, double reel type and plug-in type steel wire drawing machine are all unable to draw large-sized steel wires and hard materials because of more thread guide wheels. In order to solve this problem, a straight wire drawing machine was developed. After the steel wire is wound several times on the previous reel, it directly enters the next drawing die and is wound on the next reel without passing any thread guide wheels in the middle, and the steel wire is linear between the two reels. It adopts DC drive like the looper type, and automatically adjusts the intermediate reel speed to adapt the machine extension coefficient to the actual extension coefficient of the steel wire, that is, automatically adjusts to the normal operating point of the machine. The machine compression ratio is equal to the process compression. rate.

    The advantages of this model are simple threading, no twisting and small radius bending of the steel wire during the drawing process. Its shortcomings are that it cannot draw finer steel wires, the steel wire stays on the drum for a short time, and the cooling effect is poor; the application range of the wire drawing machine is small.

    Adjustable roller linear wire drawing machine

    This is a newer model that combines the advantages of the looper type and the straight-line wire drawing machine. It has the advantages of looper type no torsion, large speed range, high drawing speed, and good effect. It also has the advantages of simple straight-line steel wire route, convenient threading, and large-size steel wire. The steel wire has no small radius bending phenomenon in each drum, and the internal quality and surface quality of the steel wire can be greatly improved; because there is no intermediate wire guide wheel, the mechanical structure is much simplified compared with the looper type. The more advanced wire drawing machine is suitable for drawing high-strength, large-size round and special-shaped steel wires: but its large investment, complex DC speed control system, and difficult maintenance. The influence of these factors has brought a certain degree of promotion to its promotion. difficult.